The present invention relates to powered foam sprayers, and in particular, systems for controlling the discharge of foam effluents from powered foam sprayers for cleaning and for other applications.
Powered foam sprayers have long been recognized as preferred cleaning tools for commercial and industrial cleaning applications. In particular, powered foam sprayers are well suited for coating vertical and elevated surfaces with detergents and other cleaning agents without requiring time-intensive manual brush applications. The foam cleaning agents generally adhere to the surface being cleaned without premature runoff, thereby allowing the cleaning agents added time to more effectively penetrate and sanitize, while also providing the operator with a visual indication of the areas that have already been treated.
Powered foam sprayers often include a pre-mixed cleaning solution for mixing with a supply of compressed air. In these systems, the cleaning solution and the compressed air combine to form a foamy, heterogeneous mixture of gas and liquid. This heterogeneous mixture can sometimes include caustic ingredients that, while effective as a cleaner/degreaser, can be harmful when kept in contact with the human skin. Accordingly, powered foam sprayers typically include a handheld spray nozzle having a manually operated trigger. The manually operated trigger opens and closes a valve in the spray nozzle to provide control over the duration of each foam application and to guard against unintended discharge of foam spray.
Between periods of use, foam can remain captured within the spray hose under high pressure, often intentionally. For example, powered foam sprayers can in some instances rely on back pressure to stop operation of the foam sprayer. In particular, back pressure in the spray hose can be used to actuate a switch upstream of the spray nozzle (e.g. in the foam sprayer), terminating operation of the foam sprayer. More specifically, in some embodiments, the foam sprayer may be driven by a supply of compressed. A portion of the compressed air may be used to pneumatically power a pump that motivates the cleaning solution. Another portion of the air may be introduced into the system upstream from a mixing chamber so that it will mix with the cleaning solution to produce foam, and will assist in moving the foam effluent through the system. In these embodiments, the switch may be a pressure valve that closes off the supply of compressed air upstream from the pump and the mixing chamber. When the spray nozzle trigger is released, the spray nozzle valve closes and continued operation of the foam sprayer causes pressure to build in the spray hose. When the back pressure in the hose gets high enough, it closes the pressure valve, thereby effectively shutting off the foam sprayer. When the spray nozzle trigger is again opened, the pressure in the spray hose is released and the pressure valve opens, which restarts the supply of compressed air to the pump and the mixing chamber. In these types of systems, back pressure in the hose is an intended and important part of the operation of the system. It should be noted that the back pressure in the spray hose will remain even if the foam sprayer is disconnected from all sources of external power, such as the supply of compressed.
The presence of pressurized foam within the spray hose can contribute to workplace injury and can cause damage to the foam sprayer. For example, a twelve foot spray hose having a ¾ inch inner diameter can contain over one thousand cubic centimeters of foam cleaning agent, optionally under pressures greater than 300 PSI. In this regard, the spray hose remains “charged” between uses. An unknowing operator can actuate the trigger on a system that is entirely off and disconnected from a pneumatic supply line, and the foam-induced back pressure can inadvertently discharge from the spray hose. This discharge may spray against a sensitive surface, including for example the operator's hands or face, or other undesirable location. In addition, the pressurized caustic chemicals can work against the interior lining of the spray hose and against the fittings, potentially compromising the structural integrity of the spray hose or its fitting connections over time.
Accordingly, there remains a need for an improved system to leverage the benefits of existing powered foam sprayers while also guarding against inadvertent discharge of pressurized foam cleaning agents. In addition, there remains a need for an improved system for the controlled application of pressurized foam cleaning agents without requiring extensive operator training or added material costs.